Original subtitles

Black holes...

Long considered the bullies of the cosmos,

but are they really so bad?

Black holes aren't violent. They are elegant.

They're incredibly powerful objects,

but they're beautifully simple.

Simple but unpredictable.

Black holes rip planets to shreds,

but they also give birth to stars.

Black holes are like the ultimate

recycling-trash-bin combination.

They build galaxies

and may have lit up the dark infant universe.

It's one of the biggest changes that happened.

Someone switched the lights on and transforms our universe.

They come in all sizes,

from microscopic to ultramassive,

controlling the fate of everything around them.

The story of the universe and how it's arranged

is the story of black holes.

Black holes are the master architects of the universe,

and without them, we would not exist.

Black holes...

We're riveted by their destructive power.

Black holes are dangerous.

Black holes are hazards.

Black holes are not friendly for their environments.

There's just no good end to anything

that falls into a black hole.

Perhaps one of the most frightening objects

in the universe.

But what exactly are these scary objects?

Black holes are created when you get enough matter

in a small region of space.

This happens when a massive star dies

and collapses in on itself...

...a supernova.

A black hole is the ultimate consequence of gravity.

It's an object that has so much mass

crushed into such a small space that its escape velocity

becomes greater than the speed of light.

They are a one-way street.

You go in.

Nothing escapes, not even light.

But do black holes really deserve their bad rap?

In some ways, I think we set up black holes

to be more villains than they actually are.

Black holes suffer a bit of a P.R. Problem.

I think they're a lot more menacing in science fiction

and popular media than they really are.

There are trillions of galaxies in the known universe.

And most of them have a supermassive black hole

at their center.

These monsters are millions of times the mass of our sun.

Their immense gravity can send stars flying.

They're instrumental in choreographing

the dance of stars in their vicinity.

Supermassive black holes shoot out torrents

of lethal radiation and violent cosmic winds

and gobble up anything that comes close.

Now scientists are beginning to realize these cosmic giants

may also have a creative side.

Most people think of black holes

as being like giant vacuum cleaners in space,

and basically everything falls into them,

but that's not actually the case.

They're better thought of as the engines of cosmic change.

Although black holes are the end states of stars,

they can actually influence the formation of stars,

as well, in a bunch of different ways.

A galaxy's job is to make stars,

but uncontrolled star growth isn't healthy.

Too many stars can drain a galaxy's gas supply.

Black holes are very important.

It appears that galaxy evolution is tied to black-hole evolution.

We don't know exactly how yet,

but the marriage appears certain.

One idea is that supermassive black holes

act as cosmic control mechanisms.

Black holes can act like a thermostat in your house.

If your house gets too hot,

the thermostat will kick on the air conditioner,

and if it gets too cold, it'll kick on the heater.

Black holes do the same things for galaxies.

Supermassive black holes regulate star formation

by pulling gas in and shooting it back out into the galaxy.

When these black holes are consuming matter,

they're drawing matter into themselves,

but they're also spewing stuff out.

Basically, black holes eat like little babies...

Very sloppily,

so a lot of what they eat comes flying back out again.

They eat stars. They eat planets.

But most often, they eat giant clouds of gas.

The black hole drags gas and dust

into an accretion disk around it.

This disk spins faster and faster.

Magnetic energy builds up.

With the accretion disk swirling around the black hole,

there are also magnetic fields that are going on.

The material is moving so rapidly

that the magnetic field sort of winds up, coils up,

and forms a vortex like a tornado.

Astronomers call them jets.

These jets propagate outward like freight trains

plowing through the galaxy

over hundreds and thousands of light-years.

These are like death rays.

The jets disrupt the star-forming gas clouds,

limiting excess star formation in the main body of the galaxy,

but in the very outer reaches of the galaxy,

they can spark star birth.

Things are more gentle out there.

You're not as close to the energetic heart,

so stars, planets, and life can form out there

partially because of the material

that the black hole has moved out there.

So black holes can have outsize influence

on the regions that they inhabit.

Right around them, they can prevent the formation of stars

whereas, on very, very large scales,

they can actually instigate the formation of stars.

2018... black holes hit the front page.

Scientists discovered black holes gobbling up gas

so fast that they seem to be outgrowing their host galaxies.

It naturally makes the question come up...

How big can a black hole get?

Now we have the answer.

They can reach size triple-XL,

becoming ultramassive black holes.

Ultramassive black holes are so cool

because it's just mind-boggling

that black holes so large can exist.

Ultramassive black holes are very rare

and typically have masses of more than 10 billion times

the mass of the sun.

10 billion solar masses...

That's a 10 followed by nine zeros.

Ultramassive black holes are real beasts.

The black hole at the center of our galaxy

is 4 million solar masses.

Imagine black holes that are 2,500 times bigger.

That's what we're talking about here.

An ultramassive black hole this big

would be as wide as the solar system...

...and weigh as much as all the stars in the milky way.

They're inside galaxies that aren't a whole lot bigger.

That really surprised the hell out of everybody.

And in 2018, scientists discover

a 20-billion-solar-mass ultramassive black hole

growing faster than any other black hole.

This ravenous behemoth devours the mass of our sun

every two days.

These big black holes are really good

at gobbling up other things.

They'll literally eat anything.

They're monsters of the universe.

This kind of voracious eating

can have devastating consequences.

It blasts so much energy and turbulence into the galaxy

that stars no longer form,

and the bigger the black hole, the faster the galaxy dies.

The primary thing these ultramassive black holes

do to galaxies is they shut down all star formation,

and so in that sense, they kind of kill galaxies.

And so these things

could even wipe out their host galaxies.

Ultramassive black holes are a problem for scientists, too.

They might be the fastest eaters,

but that doesn't explain how they got so large.

With these ultramassive black holes,

these black holes that are 10s of billions of times

more massive than our sun, you can't just grow them

from the slow accretion of gas over time.

There's just not enough gas,

and there's just not enough time.

It gives us a new mystery to solve.

How do you make black holes that are just that big?

There's not a clear answer so far

as to how these ultramassive black holes were formed.

People wonder if there's some other mechanism

by which you could make black holes.

A mechanism so violent it also throws

supermassive black holes clean out of galaxies.

We now know that ultramassive black holes

billions of times the mass of the sun exist,

but we have no idea how they got so big.

We've detected lightweight stellar-mass

black holes colliding.

They merged into a new larger black hole

and generated huge amounts of energy.

But what about supermassive black holes?

When galaxies merge,

their central supermassive black holes

will fall to the center of the newly formed galaxy.

Could these supermassive black holes

caught up in galactic mergers

combine to form an ultramassive black hole?

In 2017, the Hubble space telescope spotted

something strange in a distant galaxy called 3c186.

It detected an incredibly bright spot

thousands of light-years from the galaxy center.

Scientists suspect it's a quasar.

A quasar is an incredibly bright, active galactic nucleus

that's powered by a supermassive black hole.

We regularly spot black-hole-powered quasars,

but always at the centers of galaxies,

until now.

When we actually got this data from Hubble,

we were absolutely stunned to discover

that the quasar that we've long known to exist

in the center of this galaxy wasn't actually at the center.

This black hole is offset from the center of the galaxy

by about 35,000 light-years.

That's really weird.

What is an incredibly rare and bizarre event

to find a quasar, a supermassive black hole,

that is not at the center of the galaxy.

When scientists looked closer,

they discovered that the quasar is hurtling through space

away from the center of the galaxy.

Now, mind you, this is a black hole

with the mass of about a billion times the sun,

and it's screaming away at 4 million miles an hour.

This black hole,

which was probably originally in the galaxy center,

has somehow been shot out at high velocity

by some incredibly violent event.

It's hard to imagine what kind of event

would pump that much energy into such a huge object

to shoot it away from the center of a galaxy.

Who kicked it out, how, and why?

Scientists have an idea.

3c186 may be the remnant of a galaxy merger.

The merged galaxies' supermassive black holes

circle each other,

sending out blasts of energy in the form of gravitational waves.

Gravitational waves are all around us.

They're ripples in the fabric of space-time.

Every time mass moves,

gravitational waves are produced,

so if I wave my hand, I am making gravitational waves.

A hand produces imperceptible waves.

When objects as huge

as supermassive black holes collide,

the energy released as gravitational waves

is phenomenal.

Scientists think these black holes

might have been different sizes.

It's possible that if one of the black holes

is really massive

and the other one isn't quite as massive,

that when they spiral around and merge,

they send out gravitational waves in an asymmetric way.

This asymmetry has a catastrophic effect.

As the two black holes collide and merge,

they shoot out a huge blast of gravitational waves,

but only in one direction.

This blast of energy kicks the newly combined black hole

out of the galactic center.

Think of a shotgun recoil, but supersized.

And there's so much energy in that emission

that it acts like a rocket,

and it actually pushes the merged black hole away.

It would have been one of the most energetic events

ever witnessed.

They're so energetic,

they are literally shaking the fabric of space.

We didn't witness the actual collision,

but 3c186 could be evidence

that supermassive black holes can collide and merge,

building even larger black holes.

This would be a mechanism by which you would create,

ultimately, an ultramassive black hole.

As for the ejected black hole,

the gravitational recoil sent it

on a one-way ride to oblivion.

So gravitational waves kicked this supermassive black hole

and sent it flying through space.

In 20 million years, it's expected to exit its galaxy.

The ejected supermassive black hole

may eventually hit another galaxy

and merge with its supermassive black hole.

These largest of black holes

seem to throw their weight around,

bullying galaxies and other black holes.

Now researchers have discovered a vampire black hole

that's draining the lifeblood of its neighbor.

Ultramassive black holes

seem to destroy their galaxies,

while supermassive black holes seem to regulate star formation.

But are all supermassive black holes forces for good?

Hundreds of galaxies surround the milky way,

large and small,

but most of the largest galaxies are red.

This is not a good omen.

In space, red means danger.

If you have active ongoing star birth,

then you have massive stars,

and massive stars tend to be blue,

but they don't live very long, and they blow up.

Once you stop star formation, after some amount of time,

the galaxy turns red.

The only stars left alive

are small, long-lived red stars called red dwarfs.

A red galaxy with only red dwarfs

is a dying galaxy.

The Sloan digital sky survey found an entire population

of these luminous red galaxies

that were no longer forming stars

that were dead.

One galaxy around 340 million light-years away stood out.

It was named after a Japanese anime character, Akira.

It's very red.

All the stars in it are red, and that means they're old,

so we know that Akira has not had

any active star formation in a long time.

The Akira galaxy doesn't form stars

because it doesn't have the cool, calm gas

needed to build them.

Something is heating the gas, making it turbulent.

One of the ways in which a black hole can drive

the evolution of the galaxy in which it resides

is by simply powering a wind.

These are winds that are literally driven by light.

When a black hole feeds,

it drags gas into an accretion disk.

The disk heats up and gives off light radiation.

The radiation pressure from the accretion disk around this black hole

couples to the ambient gas and dust

and pushes it outwards at very high velocity.

These winds that are driven out by the black hole

essentially warm up the gas in the galaxy,

preventing further star formation.

However, whatever's fueling the black hole in Akira

is a mystery.

Here's a weird thing... There is an outflow,

a wind coming out of this galaxy,

and that means there's gas feeding

that black hole in the center, and it's blowing it out.

Where is this gas coming from?

Ah, it's stealing it.

It has a small companion galaxy, which is nicknamed Tetsuo,

and that has gas in it.

Akira's supermassive black hole pulls gas from Tetsuo

and drags it into the center of the galaxy.

The black hole is taking the gas from this companion galaxy,

and that's what's falling around the black hole

and creating this wind,

so Akira is actually sort of a dead galaxy,

but it's being rejuvenated by its companion, Tetsuo.

Like a cosmic vampire,

Akira's supermassive black hole feeds off Tetsuo.

The black hole drags gas and dust into its accretion disk,

which spins faster and faster.

When these particles are rubbing against each other,

well, that generates friction.

Friction may not seem like that big of a deal.

I mean, you can rub your hands together

on a cold day to get warm,

but imagine rubbing your hands together

at very nearly the speed of light.

How much friction is that gonna generate?

It's gonna make a lot of heat.

Over a million degrees Fahrenheit...

So hot the accretion disk lights up.

Its temperature goes up, and he starts emitting light.

It becomes incredibly bright.

Even though there's a black hole in the core,

its surroundings are intensely bright.

This heats up the surrounding gas,

generating a hot wind,

which extends thousands of light-years from the black hole.

And those winds carry with them a lot of energy,

and that energy, if it couples to the gas in the galaxy,

can blow that gas out.

They inject energy into nearby gas clouds

and heat them up and prevent them from forming stars.

Stars don't form... The galaxy dies.

These dying galaxies are called red geysers.

Scientists think around 10% of the red galaxies

we see around us died this way...

...heated up by this galactic warming.

We think that the source of some of this galactic warming

is in the growth of supermassive black holes themselves

because when you grow a supermassive black hole,

you must liberate an enormous amount of energy.

You can't grow a black hole for free,

and that energy gets dumped back into the ambient surroundings

and keeps this halo of gas hot.

It prevents it from cooling and forming stars.

Sagittarius a-star,

the supermassive black hole at the heart of our galaxy,

the milky way, could turn into a red geyser.

If you were suddenly to dump an enormous amount of gas

onto Sagittarius a-star,

you could have what is effectively a red-geyser effect,

a very powerful wind driven by all of this energy.

Star formation would stop,

and our milky way would become another dying red galaxy.

Now new research suggests that Sagittarius a-star

has already affected the inner region of our galaxy,

not by killing stars,

but by transforming planets from gas giants into super-earths.

At the center of our galaxy

lies a supermassive black hole, Sagittarius a-star.

We think it's calm, dormant, safe.

Relative to other supermassive black holes

in the universe, ours is relatively quiet.

It's been active in the past,

and it could flare up in the future.

It could be active tomorrow, for all we know.

All you need to do to light it up

is start dumping some gas on it,

and there is almost certainly a giant cloud of gas

that we don't currently know of

on its way to the center of our galaxy,

and it will find itself one day in the vicinity

of our supermassive black hole,

and it will start to light up like a Christmas tree.

In February of 2018, scientists at Harvard

simulated Sagittarius a-star during a feeding frenzy

to understand the impact of an active supermassive black hole

on its local environment.

They found that,

as Sagittarius a-star gobbled up gas and dust,

it belched out bright flares of high-energy radiation,

which radically affected the region around the black hole.

The environment near the center of a galaxy

that has an actively feeding black hole

is the worst place in the universe.

You've got this tremendous object

which is heating up this gas to millions of degrees.

This is no place that you want to be.

The model revealed what would happen

to any planets in the line of fire.

Think about being in the way

of one of these black-hole burps.

All of a sudden, there's a tremendous wind of radiation

that comes through your solar system.

That could actually strip away the outer layers of gas

of a planet like Neptune.

The high-energy radiation

from the supermassive black holes

would hit the gas planets and heat up their atmospheres.

Maybe this would actually strip away the outer layers,

leaving the solid material in the middle.

You could actually turn a gas-giant planet

into a terrestrial solid planet

all because you're close to a black hole.

This radiation strips away the gas, leaving the core,

now a new rocky planet

but a giant one... A super-earth.

Normally, you think of rocky planets

being about the size of the earth,

but this would be a way of making so called super-earths.

Super-earths are one of the most common

type of planets discovered in our galaxy.

It's possible that any super-earths

close to Sagittarius a-star

were created by these blasts of energy.

Away from our galactic center,

a much smaller stellar-mass black hole

is also radically transforming its environment.

January 2017...

Researchers discover something strange

in a cloud of gas called W44.

W44 is a supernova remnant.

It's the debris... the expanding cloud from a star that blew up.

The explosive shock wave from a supernova

pushes gas and dust out from the dead star,

forming a huge nebula.

We see a lot of these.

I mean, they're catastrophic, amazing, incredible events,

but as far as they go,

this one appears to be pretty standard,

except for one weird thing.

In the heart of it,

there's something very mysterious going on.

There seems to be something shooting out

of the very center of this explosion.

A thin protrusion trillions of miles long

streams out from the cloud.

It's moving at over 60 miles a second

against the flow of the galaxy.

It's very strange that it's moving backwards

against the rotation of the milky way.

When you see a giant, giant, very massive cloud of gas

that is moving counter to the rotation of the milky way,

it needed to be like a bullet from a gun

fired against a headwind in the opposite direction.

So what is that gun?

You know, what fired that bullet of gas?

The tip of the bullet cloud is expanding

at 75 miles a second.

That's 270,000 miles an hour,

over 150 times faster than a bullet.

What in the cosmos has the power to accelerate gas

to such high speed?

Could that actually be a black hole

moving very, very quickly?

Researchers think a stellar-mass black hole

hidden in the bullet cloud

is powering the movement of the gas.

Gravity from this black hole is incredibly strong,

and so it will latch onto this gas cloud

as it passes through it,

and it can completely disrupt the motions of this cloud.

This is a very interesting stream of gas

that's somehow connected to a black hole,

and we don't know whether it's there

because the black hole is moving through the gas,

and it's creating a wake,

or whether somehow this black hole

is spitting out a stream of material in some way.

The black hole could be dragging gas

into an accretion disk around it.

The gas heats up and expands,

giving the initial supernova explosion, W44, an extra kick,

driving this bullet-like cloud out in front of it.

Or the black hole could be racing away from the nebula,

dragging the gas behind it like a wake.

Ultramassive, supermassive, and stellar-mass black holes

all play a role in shaping the cosmos,

but there may be another type of black hole

even more dangerous than the rest...

A microscopic black hole.

We have so far detected triple-XL

ultramassive black holes, large supermassive black holes,

medium-sized intermediate black holes,

and small stellar-mass black holes.

Now scientists have another to add to the roster...

Microscopic black holes.

We know there are supermassive black holes

at the centers of galaxies.

We know there are star-sized black holes

from the deaths of stars.

That's what we know for sure.

It's possible there are much smaller black holes,

microscopically small black holes.

Microscopic black holes are virtually invisible

to the naked eye,

but magnified, they look like regular stellar-mass black holes

the definition of a black hole

is an object that has so much mass

crushed into such a small space that its escape velocity

becomes greater than the speed of light,

so it could be something the size of a star,

the size of a galaxy.

It could also be the mass of a planet.

If you could crush the earth down far enough,

it could become a black hole.

The density of a black hole

is something that the human brain

really doesn't wrap itself around very easily.

When you think about something the size of the earth,

how small would the earth have to be to be a black hole?

And the answer is something on the order of a marble.

So think about taking the entire earth

and compressing it down to the size of just a marble.

So where do these strange little black holes come from?

These very small black holes can only be formed

in the exotic conditions of the incredibly early universe.

Our universe might get flooded with these small black holes

that simply persist to the present day.

It's the only time in the history of the universe

where you could take a small amount of matter

and crush it down so tightly

that it could become a black hole.

Those conditions don't exist anymore,

so if these things exist, they would be primordial.

They would be as old as the universe itself.

These primordial black holes may be ancient,

but they still pack a punch.

When it comes to black holes,

the smaller black holes are actually more dangerous

because their mass is concentrated

into such a small volume.

In fact, a tiny black hole would be lethal.

If it were to pass in front of me, very quickly,

almost instantly, I would be ripped apart head to toe,

stretched into a long, thin stream of fundamental particles

that would then wind their way into the black hole.

It would actively feast on me in a matter of seconds.

But if Paul or an interstellar robotic probe

visited a supermassive black hole

or even an ultramassive black hole,

they wouldn't be immediately ripped to shreds.

One of the most fun questions about black holes is,

how close could you get to a black hole

before the gravity would rip you apart?

And that actually depends on the volume of the black hole.

If the black hole is very large, you could get very, very close.

The more massive they are,

the slightly softer they are in how they tear things apart,

so a supermassive black hole, actually...

You can cross within the event horizon

and not really notice it.

You're never gonna get back out,

but you won't necessarily be stretched to your death

while you cross inside.

So a probe could visit a supermassive black hole

and not be destroyed...

...until it crossed the event horizon

and traveled deep inside.

Then it would be torn to pieces.

But microscopic black holes are currently just a theory.

Microscopic black holes have been the focus

for some researchers for many years,

but currently there's no evidence

to support their existence.

Microscopic primordial black holes may or may not

have been around since the big bang.

Now scientists have discovered supermassive black holes

from the very early universe.

They're shedding light on one of the most mysterious eras,

the cosmic dark ages.

Black holes don't just shape the universe now.

They've been shaping it from almost the dawn of time.

Scientists think black holes may have triggered

one of the universe's greatest transformations...

Turning from dark and foggy to transparent and light.

At the beginning of time,

the universe was a tiny ball of super-hot energy...

The big bang.

Shortly after our big bang, our universe was shining bright

because it was full of hot, glowing gas.

Then it cooled off and entered the so-called dark ages

until eventually something lit it up again.

It's one of the biggest changes that happened in our universe.

Someone switched the lights on and transformed the universe.

During the dark ages,

the universe was blanketed in a thick fog.

Then something lit it up

in a process called reionization.

We still don't really know for sure

whether reionization was mainly caused by young stars

or whether it was mainly black holes that ate stuff

and spewed out a bunch of radiation.

Then in December of 2017,

researchers in Chile scan a region of space so far away

it takes light 13 billion years to reach us.

They spot an object from just 690 million years

after the big bang

when the universe was only 5% of its current age.

It's called quasar J1342+0928.

The thing that's so amazing about this farthest quasar

is we may actually have seen the boundary of these dark ages.

This particular supermassive black hole/quasar tells us

something about the formation of the early universe.

It's thought that quasars helped drag the universe

out of the dark ages.

They gobbled up so much hydrogen gas

and belched out jets of energy

and cleared up the fog.

Those jets could have actually put so much energy

into the universe that it made it clear again.

We may actually be seeing the moment

where something punches through this boundary of the dark ages.

Pockets of reionization opened up

throughout the early universe.

They came in different sizes, depending on what created them.

While our universe was being reionized,

there was kind of, like, all these holes

that kept growing.

If the reionization was made by a large number of little stars,

you would have many, many small holes,

much like a sponge,

whereas if you had a small number

of monster black holes doing it,

you'd have a lot of big holes, like in Swiss cheese.

At present, we can't measure the ionized pockets

to determine if it was stars or black holes

that lit up the early universe.

Perhaps it was both...

Black holes and stars working together.

The more we investigate black holes,

the more we learn about their role

as architects of the universe.

I think scientists of my generation are very lucky

to be able to be at the beginning of this revolution.

We used to portray black holes as monsters.

Now we know that, without them,

the universe would be a very different place.

They made life possible.

Without black holes, we probably wouldn't exist.

We're discovering

just how black holes shaped the universe,

but the more we learn, the more questions they pose.

I've spent my career studying black holes,

and I want to spend the rest of my career studying black holes,

and I guarantee you that, at the end of my career,

on the day I retire, I will probably have

more questions about black holes than I do today.

This is an incredibly exciting time

for black-hole science.

Who knows what we're gonna discover?